Here’s a neat idea: using the standard microphone and speakers that are built into most recent laptops, researchers from Northwestern and University of Michigan have developed a sonar system to detect when a user is near the computer. Why is this interesting? Well, the idea is that it can be used to turn your computer screen off as soon as you walk away, rather than waiting the typical 10 or 20 minutes for the screensaver to kick on. It’s a pretty neat idea, especially since it doesn’t require any extra components, however I wonder how much power the sonar system itself will draw.